Vinylamine copolymer, flocculating agent etc.

ABSTRACT

Disclosed herein is a vinylamine copolymer having the structural units represented by the following formulas (I), (II), (III), (IV) and (V): ##STR1## wherein X.sup.⊖ represents an anion or hydroxyl ion, R represents a hydrogen atom or a methyl group, M.sup.⊕ represents a hydrogen ion or a monovalent cation, in which the molar fraction of the structural unit (I) is 5 to 85% by mole, the molar fraction of the structural unit (II) is 2 to 85% by mole, the molar fraction of the structural unit (III) is 5 to 80% by mole, the molar fraction of the structural unit (IV) is 0 to 40% by mole, all of said molar fractions being based on the vinylamine copolymer and the molar fraction of the structural unit (V) is 0 to 8% by mole which is based on the total content of the structural units (III), (IV) and (V), a flocculating agent and a paper strength increasing agent using the vinylamine copolymer, and a process for producing the vinylamine copolymer.

This is a continuation of copending application(s) Ser. No. 07/065,296filed on June 22, 1987 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a novel vinylamine copolymer, a flocculatingagent for the treatment of waste water using the vinylamine copolymerand a paper strength increasing agent using the vinylamine copolymer inthe paper making industry, as well as a process for producing thevinylamine copolymer. More particularly, the present invention relatesto a vinylamine copolymer having structural units represented by thefollowing formulas (I), (II), (III), (IV) and (V): ##STR2## whereinX.sup.⊖ represents an anion or hydroxyl ion, R represents a hydrogenatom or a methyl group, M.sup.⊕ represents a hydrogen ion or amonovalent cation), in which the molar fraction of the structural unit(I) is 5 to 85% by mole, the molar fraction of the structural unit (II)is 2 to 85% by mole, the molar fraction of the structural unit (III) is5 to 80% by mole, the molar fraction of the structural unit (IV) is 0 to40% by mole, all of said molar fractions being based on the vinylaminecopolymer, and the molar fraction of the structural unit (V) is 0 to 8%by mole which is based on the total content of the structural units(III), (IV) and (V), a flocculating agent for the treatment of wastewater and a paper strength increasing agent using the vinylaminecopolymer in the papermaking industry, as well as a process forproducing the vinylamine copolymer, a flocculating agent using thevinylamine copolymer, a paper strength increasing agent using thevinylamine copolymer and a process for producing the vinylaminecopolymer.

The novel vinylamine copolymer according to the present inventionexhibits excellent effects in the field of application of cationicpolymers such as flocculating agents for use in the treatment of wastewater, dehydrating agents for organic sludges, drainage aids, retentionaids, paper strength increasing agents, etc. in the papermakingindustry.

For the preparation of the polyvinylamine, a method by Hofmann reactionof polyacrylamide and hydrolysis of poly-N-vinylamide has been known.Particularly, the method of hydrolysis of a homopolymer ofN-vinylformamide is an excellent method which is capable of synthesizinga polyvinylamine of high molecular weight with high stability. However,the resultant polymer is extremely hydrophilic and has only aninsufficient effect in the case of using it as a flocculating agent fordehydration. For providing a polyvinylamine with hydrophobic properties,a method of copolymerizing N-vinylformamide and ethylene and thenhydrolyzing the resulting product has been known. However, it wasdifficult to solve the problem by use of the copolymer of N-vinylformamide and ethylene, since copolymerizability betweenN-vinylformamide and ethylene is not favorable and, in addition, it isdifficult to obtain a copolymer of high-molecular weight.

The present inventors had previously proposed a method of preparing aflocculating agent with good dehydrating properties by copolymerizingN-vinylamide with acrylonitrile, followed by hydrolysis therebymodifying not less than 10 mol % of nitrile groups into carboxyl groups[refer to Japanese Patent Application Laid Open (KOKAI) No.59-39399(1984)]. Although the effect was remarkable for N-vinylacetamidecopolymer shown in the examples, there has been a problem forN-vinylformamide copolymer in that the dehydrating property isremarkably reduced in the case where not less than 10 mol % of thenitrile groups are modified into carboxyl groups. As a result of afurther study, the present inventors had proposed a process forproducing a flocculating agent by using a basic hydrolyzate of acopolymer of N-vinylformamide and (metha)acrylonitrile [refer toJapanese Patent Application Laid Open (KOKAI) No. 61-118406(1986)].However, the proposed hydrolyzate still involves a problem in that mostof the nitrile groups are modified into carboxyl groups and, in the casewhere the content of the nitrile group in the starting copolymer ishigh, water-insoluble polymer is formed or an amphoteric polymerpredominantly containing anionic groups results and accordingly, it hadbeen difficult to reduce the water content in the dehydrated sludges inthe case of its use as a flocculating agent for dehydration.

For overcoming the foregoing drawbacks, as a result of the presentinventors' further studies, it has been found that a vinylaminecopolymer of high-molecular weight having hydrophobic properties isobtained by partially modifying a vinylformamide copolymer under acidicconditions. Such vinylamine copolymer has an excellent flocculatingeffect in the treatment of waste water and also has an excellent paperstrength increasing effect in the papermaking industry. The presentinvention has been attained based on the above findings.

SUMMARY OF THE INVENTION

In a first aspect of the present invention, there is provided avinylamine copolymer having the structural units represented by thefollowing formulas (I), (II), (III), (IV) and (V) : ##STR3## whereinX.sup.Θ represents an anion or hydroxyl ion, R represents a hydrogenatom or a methyl group, M.sup.⊕ represents a hydrogen ion or amonovalent cation, in which the molar fraction of the structural unit(I) is 5 to 85% by mole, the molar fraction of the structural unit (II)is 2 to 85% by mole, the molar fraction of the structural unit (III) is5 to 80% by mole, the molar fraction of the structural unit (IV) is to40% by mole, all of said molar fraction being based on the vinylaminecopolymer, and the molar fraction of the structural unit (V) is 0 to 8%by mole which is based on the total content of the structural units(III), (IV) and (V).

In a second aspect of the present invention, there is provided aflocculating agent comprising a vinylamine copolymer having thestructural units represented by the following formulas (I), (II), (III),(IV) and (V) : ##STR4## wherein X.sup.⊖ represents an anion or hydroxylion, R represents a hydrogen atom or a methyl group, M.sup.⊕ representsa hydrogen ion or a monovalent cation, in which the molar fraction ofthe structural unit (I) is 5 to 85% by mole, the molar fraction of thestructural unit (II) is 2 to 85% by mole, the molar fraction of thestructural unit (III) is 5 to 80% by mole, the molar fraction of thestructural unit (IV) is to 40% by mole, all of said molar fractionsbeing based on the vinylamine copolymer, and the molar fraction of thestructural unit (V) is 0 to 8% by mole which is based on the totalcontent of the structural units (III), (IV) and (V).

In a third aspect of the present invention, there is provided a paperstrength increasing agent comprising a vinylamine copolymer having thestructural units represented by the following formulas (I), (II), (III),(IV) and (V) : ##STR5## wherein X.sup.⊖ represents an anion or hydroxylion, R represents a hydrogen atom or a methyl group, M.sup.⊕ representsa hydrogen ion or a monovalent cation, in which the molar fraction ofthe structural unit (I) is 5 to 85% by mole, the molar fraction of thestructural unit (II) is 2 to 85% by mole, the molar fraction of thestructural unit (III) is 5 to 80% by mole, the molar fraction of thestructural unit (IV) is 0 to 40% by mole, all of said molar fractionsbeing based on the vinylamine copolymer, and the molar fraction of thestructural unit (V) is 0 to 20% by mole which is based on the totalcontent of the structural units (III), (IV) and (V). In a fourth aspectof the present invention, there is provided a drainage aid forpapermaking comprising a vinylamine copolymer having the structuralunits represented by the following formulas (I), (II), (III), (IV) and(V): ##STR6## wherein X.sup.⊖ represents an anion or hydroxyl ion, Rrepresents a hydrogen atom or a methyl group, M.sup.⊕ represents ahydrogen ion or a monovalent cation, in which the molar fraction of thestructural unit (I) is 5 to 85% by mole, the molar fraction of thestructural unit (II) is 2 to 85% by mole, the molar fraction of thestructural unit (III) is 5 to 80% by mole, the molar fraction of thestructural unit (IV) is 0 to 40% by mole, all of said molar fractionsbeing based on the vinylamine copolymer, and the molar fraction of thestructural unit (V) is 0 to 20% by mole which is based on the totalcontent of the structural units (III), (IV) and (V). In a fifth aspectof the present invention, there is provided a retention aid forpapermaking comprising a vinylamine copolymer having the structuralunits represented by the following formulas (I), (II), (III), (IV) and(V): ##STR7## wherein X.sup.⊖ represents an anion or hydroxyl ion, Rrepresents a hydrogen atom or a methyl group, M.sup.⊕ represents ahydrogen ion or a monovalent cation, in which the molar fraction of thestructural unit (I) is 5 to 85% by mole, the molar fraction of thestructural unit (II) is 2 to 85% by mole, the molar fraction of thestructural unit (III) is 5 to 80% by mole, the molar fraction of thestructural unit (IV) is 0 to 40% by mole, all of said molar fractionsbeing based on the vinylamine copolymer, and the molar fraction of thestructural unit (V) is 0 to 20% by mole which is based on the totalcontent of the structural units (III), (IV) and (V). In a sixth aspectof the present invention, there is provided a process for producing avinylamine copolymer having structural units comprising the followingformulas (I), (II), (III), (IV) and (V): ##STR8## wherein X.sup.⊖represents an anion or hydroxyl ion, R represents a hydrogen atom or amethyl group, M.sup.⊕ represents a hydrogen ion or a monovalent cation,in which the molar fraction of the structural unit (I) is 5 to 85% bymole, the molar fraction of the structural unit (II) is 2 to 85% bymole, the molar fraction of the structural unit (III) is 5 to 80% bymole, the molar fraction of the structural unit (IV) is to 40% by mole,all of said molar fractions being based on the vinylamine copolymer, andthe molar fraction of the structural unit (V) is 0 to 8% by mole whichis based on the total content of the structural units (III), (IV) and(V), which comprises polymerizing a mixture of N-vinylformamide and acompound of the following general formula (VI)

    CH.sub.2 =CR-CN                                            (VI)

(wherein R represents a hydrogen atom or a methyl group) at a molarratio from 20:80 to 95:5 under the presence of a radical polymerizationinitiator, and then modifying formyl groups in the resultant polymerunder acidic conditions.

DETAILED DESCRIPTION OF THE INVENTION

The vinylamine copolymer according to the present invention has thestructural units represented by the formulas (I), (II), (III), (IV) and(V): ##STR9## (wherein X.sup.⊖ represents an anion or hydroxyl ion, Rrepresents a hydrogen atom or a methyl group, M.sup.⊕ represents ahydrogen ion or a monovalent cation), in which the molar fraction of thestructural unit (I) is 5 to 85% by mole, the molar fraction of thestructural unit (II) is 2 to 85% by mole, the molar fraction of thestructural unit (III) is 5 to 80% by mole, the molar fraction of thestructural unit (IV) is 0 to 40% by mole, all of said molar fractionsbeing based on the vinylamine copolymer, and the molar fraction of thestructural unit (V) is 0 to 8% by mole which is based on the totalcontent of the structural units (III), (IV) and (V).

A preferred structural unit composition for the copolymer according tothe present invention is: from 5 to 85 mol % of the structural unit (I)in the molar fraction, from 2 to 85 mol % of the structural unit (II) inthe molar fraction, from 5 to 60 mol % of the structural unit (III) inthe molar fraction, from 0 to 30 mol % of the structural unit (IV) inthe molar fraction, all of said molar fractions being based on thevinylamine copolymer, and from 0 to 5 mol % of the structural unit (V)in the molar fraction which is based on the total content of thestructural units (III), (IV) and (V), and a particularly preferredstructural unit composition is: from 5 to 85 mol % of the structuralunit (I) in the molar fraction, from 5 to 60 mol % of the structuralunit (II) in the molar fraction, from 10 to 60 mol % of the structuralunit (III) in the molar fraction, from 0 to 30 mol % of the structuralunit (IV) in the molar fraction, all of said molar fractions being basedon the vinylamine copolymer, and from 0 to 2.5 mol % of the structuralunit (V) in the molar fraction which is based on the total content ofthe structural units (III), (IV) and (V).

The novel vinylamine copolymer according to the present invention is awater soluble polymer having a reduced viscosity from 0.1 to 10 dl/g,preferably from 0.5 to 10 dl/g measured as a solution thereof preparedby dissolving the copolymer in aqueous 1N sodium chloride solution to aconcentration of 0.1 g/dl at a temperature of 25° C.

The novel vinylamine copolymer according to the present invention can beeasily obtained by modifying the formyl groups in an N-vinylformamidecopolymer under acidic conditions. The N-vinylformamide copolymer usedas the starting material is a copolymer prepared by polymerizing amixture of N-vinylformamide and a compound represented by the followinggeneral formula (VI)

    CH.sub.2 =CR-CN                                            (VI)

(wherein R represents a hydrogen atom or a methyl group), that is,acrylonitrile or methacrylonitrile at a molar ratio from 20:80 to 95:5,preferably, from 40:60 to 95:5 and, more preferably, from 40:60 to90:10, in the presence of a radical polymerization initiator. It is,preferably, a copolymer of N-vinylformamide and acrylonitrile.

As a polymerization method for producing the N-polyvinylamide copolymer,there can be used mass polymerization, solution polymerization orprecipitation polymerization using various solvents, and aqueoussolution polymerization or the precipitation polymerization whichinitiates the polymerization by using an aqueous solution of the monomeris preferred. In the case of polymerizing the monomer in the form of anaqueous solution, the monomer concentration, polymerization method and apolymerizing reactor are properly selected in consideration with themolecular weight of an objection polymer and the calorific control fromheat of polymerization. The polymerization is conducted, for example, bythe following method: (1) a method of polymerizing in a state ofsolution with a monomer concentration of from 5 to 20% by weight andpreparing the polymer as a precipitate, (2) a method of polymerizing ina state of hydrous gel with a monomer concentration of from 20 to 60% byweight and preparing the copolymer as a hydrous gel-like product orprecipitate, (3) a method of polymerizing an aqueous solution of themixture with a monomer concentration of 20 to 60% by weight in a stateof an oil-in-water or water-in-oil type emulsion by using a hydrophobicsolvent and an emulsifier, and (4) a method of polymerizing an aqueoussolution of the mixture with a monomer concentration of 20 to 60% byweight in a state of a water-in-oil type dispersion by using ahydrophobic solvent and a dispersion stabilizer, etc. A particularlypreferred polymerization method is precipitation polymerization inwater.

As the radical polymerization initiator, there can be used any of theordinary initiators which are commonly used for the polymerization ofwater-soluble or hydrophilic monomers. Azo compounds are preferred forproducing a polymer in high yield. Particularly preferred arewater-soluble azo compounds, for example, hydrochlorides and acetates of2,2═-azobis-2-amidinopropane; sodium salt of 4,4═-azobis-4-cyanovalericacid; and hydrochlorides and sulfates of azobis-N,N═-dimethyleneisobutylamidine. The amount of the polymerization initiator used isusually within a range from 0.01 to 1% by weight based on the weight ofthe monomer. Further, the polymerization reaction is usually carried outunder an inert gas stream at a temperature from 30° to 100° C.

The thus obtained N-vinylformamide copolymer can be modified in the formit is, in a solution, in a dispersion or in a dilute solution of thepolymer or in a powder obtained by dehydrating or drying the polymer inthe known method, under acidic conditions, whereby the novelpolyvinylamine can be obtained. While on the other hand, in the casewhere the resultant N-vinylformamide copolymer is subjected to basichydrolysis in water, nitrile groups in the polymer are substantiallyeliminated. Particularly, in the case where the content of the nitrilegroup in the polymer is high, it tends to result in an insoluble polymeror an amphoteric copolymer predominantly containing anionic groups.

As the modification method for the N-vinylformamide copolymer, there canbe mentioned, for example, (1) a method of hydrolyzing in water underacidic conditions, (2) a method of hydrolyzing in a hydrophilic solventsuch as water-containing alcohol, and (3) a method for subjecting toalcohol-addition degration and modifying formyl groups while separatingas an ester of formic acid. As the alcohols in the case ofalcohol-addition degration, those alcohols of 1 to 4 carbon atoms can bementioned and methanol is preferred. The structural unit (V) maypartially be converted into esters depending on the case by thealcohol-addition degration, but the effect of the copolymer according tothe present invention does not substantially change even when itcontains not more than 5 mol % of esters.

As the modifying agent used in the case of the acidic modification, anystrongly acidic compounds can be used such as, hydrochloric acid, bromicacid, hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid,sulfamic acid and alkanesulfonic acid. The amount of the modifying agentused may properly be selected from a range of 0.1 to 2 times to themolar quantity of the formyl groups in the polymer according to thedesired rate of modification. The modifying reaction is usually carriedout under temperature conditions of from 40 to 100° C., by which a novelvinylamine copolymer containing nitrile groups in the molecules with lowcarboxyl group content and having preferable water solubility is formed.

The vinylamine copolymer according to the present invention exhibits anexcellent effect as a cationic flocculating agent for the treatment ofwaste water for flocculating organic suspensions, a flocculating agentfor the dehydration of organic sludges, etc. Particularly, it exhibitsan excellent effect as a dehydrating fluocculating agent for primarysettled raw sludges in the treatment of sewage, sludges produced by theactivated sludge treatment of water soluble organic materials, thesludges produced in the aerophobic treatment of water soluble organicmaterials and mixtures thereof. The novel vinylamine copolymer is usedin the same manner as in the method of using the conventional cationicflocculating agent, for example, polymers of dimethylaminoethylmethacrylate. That is, the vinylamine copolymer is used in the form of a0.1-0.5% by weight aqueous solution, and it is added and mixed in anorganic sludge-containing suspension in an amount of 20 to 20,000 ppmbased on the weight of the suspention.

In the case of using the vinylamine copolymer according to the presentinvention as a flocculating agent, it is preferred that the vinylaminecopolymer is a water soluble polymer having a reduced viscosity of 1 to10 dl/g measured as a solution thereof prepared by dissolving thecopolymer in aqueous 1N sodium chloride solution to a concentration of0.1 g/dl at a temperature of 25° C. Since the organic sludges subjectedto the flocculating treatment by using the vinylamine copolymeraccording to the present invention are formed more firm and solid flocksthan in the case of using a polymer obtained by modifying a homopolymerof N-vinylformamide, the dehydrating speed is improved, the throughputrate is increased and the water content in the dehydrated sludges isreduced by subjecting to machine dehydration such as compressiondehydration, centrifuging vacuum filtration etc. by use of a belt press,screw press, filter press, etc.

The vinylamine copolymer according to the present invention can be usedalso as a cationic water-soluble polymer for the papermaking industryand exhibits an excellent effect in use as a drainage aid, retention aidand paper strength increasing agent. In the case of using the vinylaminecopolymer for these applications, a water-soluble polymer having areduced viscosity of 0.5 to 10 dl/g measured as a solution thereof isprepared by dissolving the copolymer in 1N aqueous sodium chloridesolution to a concentration of 0.1 g/dl at a temperature of 25° C.

Also, for using the vlnylamine copolymer as a drainage aid, a retentionaid and a paper strength increasing agent, 0 to 8% by mole of thestructural unit (V) in the molar fraction based on the total content ofthe structural units (III) to (V) is preferred. However, the molarfraction of the structural unit is not restricted to the above-mentionedvalue. The molar fraction of the structural unit (V) of 0 to 20% by molebased on the total content of the structural units (III) to (V) can beadapted. It can be used by any of the known papermaking methods. Thatis, a cationic polymer of an amount equivalent to 0.05-2% by weightbased on the dry weight of pulp is added as a 0.1-5 wt % aqueoussolution to a pulp slurry containing 0.5-3 wt % of pulp and thensubjected to a papermaking step. Particularly, in the case of using thepolymer of the present invention as a paper strength increasing agent, amethod of adding it to the pulp slurry as an internal additive to thepulp slurry may be used, or it may be coated onto wet or dry web by aroll coater, size press or dipping machine. If necessary, cationicstarch, aluminum sulfate and anionic polyacrylamide may be used jointlywith the polymer of the present invention. It can be used with groundpulp, sulfide pulp, craft pulp and beaten wastepaper with no restrictionto the type of the pulps.

The cationic polymer is extremely stable in the form of an aqueoussolution irrespective of the quality of the solution in which thepolymer is dissolved or even if in a diluted aqueous solution. Further,it is stable and does not lose its effect even under weakly alkalinepaper-making conditions when using calcium carbonate as a filler. Theadditive is excellent under neutral or weakly alkaline papermakingconditions.

The novel vinylamine copolymer containing nitrile groups in the moleculeaccording to the present invention contributes much to the field ofapplying flocculating agents and papermaking additives.

The present invention will now be described in more detail by way ofexamples, but it should be noted that the invention is in no way limitedto the following examples.

Examples (A1-A10) of Preparation of N-Vinylamine Copolymer

Into a 50 ml four-necked flask equipped with a stirrer, a nitrogenintroduction tube and a cooling tube, 39.9 g of an aqueous solutioncontaining 4.0 g of a mixture of each of the monomer compositions asshown in Table 1 was charged. After increasing the temperature to 60° C.under stirring in a nitrogen gas stream, 0.12 g of 10 wt % aqueoussolution of 2,2═-azobis-2-amidinopropane dihydrochloride was added. Theresultant mixture was maintained under stirring at 60° C. for threehours to obtain a suspension in which a polymer was precipitated inwater. The remaining monomer in the water was measured by liquidchromatography to calculate the composition of the polymer.

A concentrated hydrochloric acid in an amount equivalent to molarquantity of formyl groups in the polymer was added and maintained understirring at 75° C. for 8 hours to hydrolyze the polymer. The solution ofthe resultant polymer was added in acetone to precipitate the polymer,which was dried in vacuum to obtain a solid polymer (hereinafterreferred to as polymer A-J).

Each of the compositions of the formed products was determined based onthe composition of the copolymer before hydrolysis, the colloidalequivalent value of the product, the atomic ratio for carbon, nitrogenand chlorine based on the elemental analysis, as well as the ¹³ C-NMRspectrum shown together with the reduced viscosity of the product.

Measurement for the Colloidal Equivalent Amount

Solid polymer was dissolved into distilled water to a concentration of0.1% by weight. After diluting 5.0 g of the aqueous solution by into 200ml of desalted water and adjusting pH value of the solution to 3 byusing a diluted hydrochloric acid, the colloidal equivalent value wasdetermined by the colloidal titration method by using 1/400 N polyvinylpotassium sulfate and using toluidine blue as an indicator.

Measurement for the Reduced Viscosity

The solid polymer was dissolved in 1N aqueous solution of sodiumchloride to a concentration of 0.1 g/dl, and the reduced viscosity at25° C. was measured by using an Ostwald viscometer.

Reduced viscosity (dl/g)=(t-t₀)/t₀ /0.1 (wherein t₀ representsdescending speed of aqueous sodium chloride and t represents descendingspeed of polymer solution).

                  TABLE 1                                                         ______________________________________                                                Monomer composition (mol %)                                           Example   VF.sup.1      AN.sup.2                                                                             AC.sup.3                                       ______________________________________                                        A1        90            10     0                                              A2        75            25     0                                              A3        60            40     0                                              A4        60            40     0                                              A5        50            50     0                                              A6        40            60     0                                              A7        40            60     0                                              A8        50            50     0                                              A9        50            46.5   3.5                                             A10      50            45     5                                              ______________________________________                                         Note:                                                                         .sup.1 VF: Nvinylformamide                                                    .sup.2 AN: acrylonitrile                                                      .sup.3 AC: sodium acrylate                                               

                  TABLE 2                                                         ______________________________________                                                                    Reduced                                                     Structural unit of the product                                                                  visco-                                                      (mol %)           sity                                              Example                                                                              Polymer  I      II   III   IV   V    (dl/g)                            ______________________________________                                        A1     A        75     15    8     2   0    1.9                               A2     B        64     11   18     7   0    2.5                               A3     C        57      3   25    14   1    3.6                               A4     D        30     30   34     6   0    2.0                               A5     E        33     17   35    14   1    2.5                               A6     F        35      5   30    29   1    3.1                               A7     G        17     23   47    11   2    2.5                               A8     H        46      4   32    16   2    3.0                               A9     I        32     18   33    13   4    2.8                                A10   J        31     19   32    12   6    2.9                               ______________________________________                                         Note:                                                                         0.5 eq of hydrochloric acid was used to the formyl groups in the polymer      upon modification in Examples A4 and A7.                                      Modifying reaction was carried out at 95° C. in Example A8. X is       chlorine ion in the structural unit (I), and R and M are hydrogen atom in     the structural units (III) and (V).                                      

Comparative Example of preparation of N-Vinylamine Copolymer

The procedures are the same as those in Example A5 except for using oneequivalent of an aqueous 40% sodium hydroxide solution to the formylgroups of the N-vinylformamide copolymer instead of concentratedhydrochloric acid in Example 5. The resultant polymer was a slightlysoluble amphoteric copolymer not substantially containing the nitrilegroups.

Examples B1-B7 and Comparative Example B8-B10 (Flocculating Properties)

100 ml (2.0% by weight of solid content) of mixed raw sludges obtainedfrom the city sewage treatment plant were put into a 200 ml -polyethylene beaker and 6 ml of an aqueous 0.2 wt. % solution of each ofthe polymers shown in Table 3 was added thereto. The suspension wasagitated by using a stirrer having at its end three rods 5 mm indiameter and 20 mm in length a at a speed of 1000 rpm for 10 sec. Theflocculated sludges were charged in a cylinder bottomed with a 60 meshnylon screen having a diameter of 65 mm and subjected to gravityfiltration, and after 10 sec, the amount of the filtrate was measured.Further, a portion of the gravity-filtered sludges was charged in acentrifuging basket having a dish drainer at the bottom and centrifugedat a speed of 3000 rpm for 30 sec for dehydration. The sludges after thedehydration were dried at 110° C. for 6 hours and the solid content weremeasured to calculate the water content in the sludges aftercentrifuging dehydration.

While on the other hand, the sludges are gravity-filtered under the sameconditions as described above. The sludges after the filtration were putbetween polyester filter cloths, which were put between polyvinylchloride plates provided with draining grooves and dehydrated by ahydraulic press having a piston of 20 mm in diameter under theconditions of a piston pressure at 50 kg/cm² for 30 sec. The sludgesafter the dehydration were dried at 110° C. for 6 hours and the solidcontents were measured to calculate the water contents in the sludgesafter the press dehydration.

These results are shown collectively in Table 3.

                                      TABLE 3                                     __________________________________________________________________________                 Amount of                                                                            Water content                                                                          Water content                                                 filtrate                                                                             of sludges                                                                             of sludges                                       Example      10 sec. after                                                                        after    after                                            and          the gravity                                                                          centrifuging                                                                           press-                                           Comparative  filtration                                                                           dehydration                                                                            dehydration                                      Example                                                                              Polymer                                                                             (ml)   (wt %)   (wt %)                                           __________________________________________________________________________    B1     A     55     78.2     75.4                                             B2     B     60     78.4     75.2                                             B3     C     60     78.0     74.6                                             B4     E     65     77.6     74.6                                             B5     F     65     77.2     74.4                                             B6     H     65     77.0     73.8                                             B7     I     60     78.8     75.6                                             B8     J     55     81.6     77.8                                             B9     .sup. K.sup.1                                                                       45     83.4     80.5                                              B10   .sup. L.sup.2                                                                       not    --       --                                                            agulated                                                         __________________________________________________________________________     (Note)                                                                        .sup.1 Polymer K: Copolymer of 2methacryloyloxyethyl trimethyl ammonium       chloride and acrylamide (molar ratio: 2/8) (reduced viscosity: 10.7 dl/g)     .sup.2 Polymer L: Hydrolyzate of Nvinylamide  ethylene copolymer (molar       ratio: 56/44) Modification ratio: 59 mol %, reduced viscosity: 0.2 dl/g  

Examples C1-C9 and Comparative Example C10 (Paper Strength IncreasingEffects)

A 0.6% LBKP slurry having freeness of 400 ml measured by CanadianStandard was present together with calcium carbonate in an amount of 17%based on the pulp, and the mixture was put into a 500 ml-beaker. Afteradding the chemicals shown below in the form of an aqueous solutionunder stirring, papers of 60 g of basis weight were made by using aTAPPI Standard square type paper machine, pH value upon paper makingbeing 8.5.

    ______________________________________                                        (Condition of Using Added Chemicals)                                                       Concentration                                                                 of aqueous                                                                              Addition amount                                                     solution  to pulp dry weight                                                  (wt %)    (wt %)                                                 ______________________________________                                        Cationic starch                                                                              1.0         0.5                                                Polymers A-G, I and J                                                                        0.5         0.5                                                Sizing agent   1.0         0.2                                                (alkyl ketene dimer)                                                          Filler retention improving                                                                   0.1          0.02                                              agent                                                                         ______________________________________                                    

For the comparison, paper was made in the same manner without adding anyof the polymers A14 G, I and J among the added chemicals.

The thus obtained wet papers were dried for three minutes by using adrum drier at 120° C. After allowing to stand the resultant papers underthe conditions of a temperature of 20° C. and relative humidity of 60%,the specific burst factor and the burst length were measured accordingto JIS-P 8112 and JIS-P 8113. ##EQU1## where

S₁ : burst strength (kg/cm²)

W: basis weight of test paper (g/m²)

S₂ : tensile strength (kg)

B: width of the test piece (mm)

The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                             Specific burst                                                                factor     Burst length                                  Example   Polymer    (Kg/cm.sup.2)                                                                            (Km)                                          ______________________________________                                        C1        A          1.46       2.55                                          C2        B          1.47       2.54                                          C3        C          1.63       2.69                                          C4        D          1.57       2.38                                          C5        E          1.39       2.44                                          C6        F          1.39       2.17                                          C7        G          1.38       2.40                                          C8        I          1.42       2.38                                          C9        J          1.35       2.21                                          Compara-  not        1.12       1.92                                          tive      added                                                               Example                                                                       C10                                                                           ______________________________________                                    

Examples C11-C19 and Comparative Example C20 (Paper Strength IncreasingEffects)

1% slurry of waste liner boar paper having a freeness of 300 ml measuredby Canadian Standard was put into a 500 ml-beaker and an aqueous 0.5 wt.% solution of each of the polymers A-G was added in an amount of 0.3% byweight based on the dry weight of the pulp and then the resultantmixture was maintained for one minute. Papers of basis weight of 120 gwere made by using a TAPPI Standard square type paper machine. Aftertreating the thus resultant wet papers in the same procedures as inExample C1, the paper strength of the resultant papers was measured. Forthe comparison, paper was made in the same procedures as above butwithout adding any of the polymers and the strength of the resultantpaper was measured. The results are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                              Specific burst factor                                   Example      Polymer  (Kg/cm.sup.2)                                           ______________________________________                                        C11          A        2.51                                                    C12          B        2.71                                                    C13          C        2.72                                                    C14          D        2.71                                                    C15          E        2.86                                                    C16          F        2.82                                                    C17          G        2.71                                                    C18          I        2.76                                                    C19          J        2.52                                                    Compara-     not      2.26                                                    tive         added                                                            Example                                                                       C20                                                                           ______________________________________                                    

Examples D1-D9 and Comparative Example D10 (Drainage Aid Effects forPapermaking)

One liter of 0.3% slurry of LBKP having a freeness of 220 ml measured byCanadian Standard was put into a 2 liter-beaker and each of the polymersA-G, I and J in the form of 0.2 wt. % aqueous solution was added in anamount of 0.2% by weight based on the dry weight of the pulp understirring. After stirring the mixture at a speed of 200 rpm for oneminute, the freeness of each product was measured by using a CanadianFreeness Tester. For the comparison, an experiment was conducted in thesame way without adding any of the polymers. The results are shown inTable 6.

                  TABLE 6                                                         ______________________________________                                        Example       Polymer  Freeness (ml)                                          ______________________________________                                        D1            A        270                                                    D2            B        260                                                    D3            C        300                                                    D4            D        285                                                    D5            E        285                                                    D6            F        255                                                    D7            G        250                                                    D8            I        280                                                    D9            J        260                                                    Compara-      not      220                                                    tive          added                                                           Example                                                                       D10                                                                           ______________________________________                                    

Examples E1-E9 and Comparative Example E10 (Retention Aid Effects forPapermaking)

One liter of 0.5% LBKP slurry having a freeness of 410 ml measured byCanadian Standard was put into a 2 liter-beaker and 30% by weight ofpapermaking talc, 0.3% by weight of reinforcing rosin and 4% by weightof aluminum sulfate based on the dry weight of the pulp wererespectively added under stirring. Further, after adding an aqueous 0.2wt. % solution of each of the polymers A-G, I and J in an amount of0.03% by weight based on the pulp and stirring at a speed of 200 rpm forone minutes, papers of 70 g basis weight were made by the sameprocedures as in Example C1.

The ash content in the thus obtained resultant papers were measured andthe results are shown in Table 7.

For the comparison, paper was made in the same procedures but withoutadding any of the polymers.

                  TABLE 7                                                         ______________________________________                                        Example       Polymer  Ash content (%)                                        ______________________________________                                        E1            A        15.7                                                   E2            B        15.6                                                   E3            C        17.1                                                   E4            D        18.0                                                   E5            E        16.7                                                   E6            F        16.5                                                   E7            G        15.7                                                   E8            I        15.5                                                   E9            J        15.0                                                   Comparative   not      12.7                                                   Example       added                                                           E10                                                                           ______________________________________                                    

What is claimed is:
 1. A vinylamine copolymer having the structural units represented by the following formulas (I), (II), (III), (IV) and (V): ##STR10## wherein X.sup.⊖ represents an anion, R represents a hydrogen atom or a methyl group, M.sup.⊕ represents a hydrogen ion or a monovalent cation, in which the molar fraction of the structural unit (I) is 5 to 85% by mole, the molar fraction of the structural unit (II) is 2 to 85% by mole, the molar fraction of the structural unit (III) is 5 to 80% by mole, the molar fraction of the structural unit (IV) is 0 to 40% by mole, all of said molar fractions being based on the vinylamine copolymer, and the molar fraction of the structural unit (V) is 0 to 8% by mole which is based on the total content of the structural units (III), (IV) and (V) and the total of the molar fractions of the structural units I-V is equal to 100%.
 2. A vinylamine copolymer according to claim 1, wherein the reduced viscosity of the vinylamine copolymer is from 0.1 to 10 dl/g measured as a solution thereof prepared by dissolving said copolymer in an aqueous 1N sodium chloride solution to a concentration of 0.1 g/dl at 25° C.
 3. A vinylamine copolymer according to claim 1, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 2 to 85 mol % of the structural unit (II) in the molar fraction, from 5 to 60 mol % of the structural unit (III) in the molar fraction, from 0 to 30 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 5 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 4. A vinylamine copolymer according to claim 3, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 5 to 60 mol % of the structural unit (II) in the molar fraction, from 10 to 60 mol % of the structural unit (III) in the molar fraction, from 0 to 30 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 2.5 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 5. A flocculating agent comprising a vinylamine copolymer having the structural units represented by the following formulas (I), (II), (III), (IV) and (V): ##STR11## wherein X.sup.⊖ represents an anion or hydroxyl ion, R represents a hydrogen atom or a methyl group, M.sup.⊕ represents a hydrogen ion or a monovalent cation, in which the molar fraction of the structural unit (I) is 5 to 85% by mole, the molar fraction of the structural unit (II) is 2 to 85% by mole, the molar fraction of the structural unit (III) is 5 to 80% by mole, the molar fraction of the structural unit (IV) is 0 to 40% by mole, all of said molar fractions being based on the vinylamine copolymer, and the molar fraction of the structural unit (V) is 0 to 8% by mole which is based on the total content of the structural units (III), (IV) and (V), and the total of the molar fractions of the structural units I-V is equal to 100%.
 6. A flocculating agent according to claim 5, wherein the reduced viscosity of the vinylamine copolymer is from 0.1 to 10 dl/g measured as a solution thereof prepared by dissolving said copolymer in an aqueous 1N sodium chloride solution to a concentration of 0.1 g/dl at 25° C.
 7. A flocculating agent according to claim 5, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 2 to 85 mol % of the structural unit (II) in the molar fraction, from 5 to 60 mol % of the structural unit (III) in the molar fraction, from 0 to 30 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 5 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 8. A flocculating agent according to claim 7, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 5 to 60 mol % of the structural unit (II) in the molar fraction, from 10 to 60 mol % of the structural unit (III) in the molar fraction, from 0 to 30 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 2.5 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 9. A paper strength increasing agent comprising of a vinylamine copolymer having the structural units represented by the following formulas (I), (II), (III), (IV) and (V): ##STR12## wherein X.sup.⊖ represents an anion or hydroxyl ion, R represents a hydrogen atom or a methyl group, M.sup.⊕ represents a hydrogen ion or a monovalent cation, in which the molar fraction of the structural unit (I) is 5 to 85% by mole, the molar fraction of the structural unit (II) is 2 to 85% by mole, the molar fraction of the structural unit (III) is 5 to 80% by mole, the molar fraction of the structural unit (IV) is 0 to 40% by mole, all of said molar fractions being based on the vinylamine copolymer, and the molar fraction of the structural unit (V) is 0 to 20% by mole which is based on the total content of the structural units (III), (IV) and (V), and the total of the molar fractions of the structural units I-V is equal to 100%.
 10. A paper strength increasing agent according to claim 9, wherein the reduced viscosity of the vinylamine copolymer is from 0.1 to 10 dl/g measured as a solution thereof prepared by dissolving said copolymer in an aqueous 1N sodium chloride solution to a concentration of 0.1 g/dl at 25° C.
 11. A paper strength increasing agent according to claim 9, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 2 to 85 mol % of the structural unit (II) in the molar fraction, from 5 to 80 mol % of the structural unit (III) in the molar fraction, from 0 to 40 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 8 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 12. A paper strength increasing agent according to claim 11, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 5 to 60 mol % of the structural unit (II) in the molar fraction, from 10 to 60 mol % of the structural unit (III) in the molar fraction, from 0 to 30 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 2.5 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 13. A drainage aid for papermaking comprising of a vinylamine copolymer having the structural units represented by the following formulas (I), (II), (III), (IV) and (V): ##STR13## wherein X.sup.⊖ represents an anion or hydroxyl ion, R represents a hydrogen atom or a methyl group, M.sup.⊕ represents a hydrogen ion or a monovalent cation, in which the molar fraction of the structural unit (I) is 5 to 85% by mole, the molar fraction of the structural unit (II) is 2 to 85% by mole, the molar fraction of the structural unit (III) is 5 to 80% by mole, the molar fraction of the structural unit (IV) is 0 to 40% by mole, all of said molar fractions being based on the vinylamine copolymer, and the molar fraction of the structural unit (V) is 0 to 20% by mole which is based on the total content of the structural units (III), (IV) and (V), and the total of the molar fractions of the structural units I-V is equal to 100%.
 14. A drainage aid according to claim 13, wherein the reduced viscosity of the vinylamine copolymer is from 0.1 to 10 dl/g measured as a solution thereof prepared by dissolving said copolymer in an aqueous 1N sodium chloride solution to a concentration of 0.1 g/dl at 25° C.
 15. A drainage aid according to claim 13, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 2 to 85 mol % of the structural unit (II) in the molar fraction, from 5 to 80 mol % of the structural unit (III) in the molar fraction, from 0 to 40 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 8 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 16. A drainage aid according to claim 15, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 5 to 60 mol % of the structural unit (II) in the molar fraction, from 10 to 60 mol % of the structural unit (III) in the molar fraction, from 0 to 30 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 2.5 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 17. A retention aid for papermaking comprising of a vinylamine copolymer having the structural units represented by the following formulas (I), (II), (III), (IV) and (V): ##STR14## wherein X.sup.⊖ represents an anion or hydroxyl ion, R represents a hydrogen atom or a methyl group, M.sup.⊕ represents a hydrogen ion or a monovalent cation, in which the molar fraction of the structural unit (I) is 5 to 85% by mole, the molar fraction of the structural unit (II) is 2 to 85% by mole, the molar fraction of the structural unit (III) is 5 to 80% by mole, the molar fraction of the structural unit (IV) is 0 to 40% by mole, all of said molar fractions being based on the vinylamine copolymer, and the molar fraction of the structural unit (V) is 0 to 20% by mole which is based on the total content of the structural units (III), (IV) and (V), and the total of the molar fractions of the structural units I-V is equal to 100%.
 18. A retention aid according to claim 17, wherein the reduced viscosity of the vinylamine copolymer is from 0.1 to 10 dl/g measured as a solution thereof prepared by dissolving said copolymer in an aqueous 1N sodium chloride solution to a concentration of 0.1 g/dl at 25° C.
 19. A retention aid according to claim 17, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 2 to 85 mol % of the structural unit (II) in the molar fraction, from 5 to 80 mol % of the structural unit (III) in the molar fraction, from 0 to 40 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 8 mol % of the structural unit (V) in the molar fraction which is based on the total content of the structural units (III), (IV) and (V).
 20. A retention aid according to claim 19, wherein the composition of said vinylamine copolymer is from 5 to 85 mol % of the structural unit (I) in the molar fraction, from 5 to 60 mol % of the structural unit (II) in the molar fraction, from 10 to 60 mol % of the structural unit (III) in the molar fraction, from 0 to 30 mol % of the structural unit (IV) in the molar fraction, all of said molar fractions being based on the vinylamine copolymer, and from 0 to 2.5 mol % of the structural unit (V) in the molar fraction based on the total content of the structural units (III), (IV) and (V). 